Application of mathematical models to predict the drying kinetics of energy cane
Laura Marcela Guiffo-Cardona1; Melina Gesteira Souza1; Kátia Tannous1; Caio Glauco Sanchez1
1 State University of Campinas
doi:10.20906/CPS/COB-2015-1494
Resumo
This study evaluates the isothermal drying of the energy cane Saccharum spontaneum as a pre-treatment of pyrolysis process, fitting the kinetic parameters and analyzing the activation energy required. The isothermal drying tests were performed in a forced air oven applying four temperatures: 30°C, 60°C, 90ºC, and 103°C. Saccharum spontaneum samples were shaped as cylinders with diameter of 0.01 m and length around 0.05 m. The moisture loss curves were fitted using semi-theoretical models (Lewis, Logarithmic, Henderson & Pabis). The activation energy and the pre-exponential factor were determined with two methods. In the first method, the parameter K of the semi-theoretical models was linearized as a function of the temperature obtaining the activation energy and the pre-exponential factor according to Arrhenius law. Values between 27-29 kJ/mol for the activation energy and 4.5-8.4 s-1 for the pre-exponential factor were obtained. In the second one, the calculation was done by Arrhenius law and Fick's law considering the dependency of the effective diffusivity coefficient and the temperature. In this case, an infinite cylinder geometry was assumed observing a effective diffusivity range between 1×10-10 and 5.2×10-9m2/s for all temperatures. Values of 23.9 kJ/mol for the activation energy and 1.07×10-5 m2/s for the pre-exponential factor were obtained. Therefore, this shows that the kinetic parameters were quite lower for the second method since the consideration was limited by radial mass transfer.
Palavras-chave: Arrhenius law; Biomass; Effective diffusivity ; Fick´s second law; semi-theoretical model